Variable valve timing mechanism



Oct. l, 1968 F. A. WAGNER VARIABLE VALVE TIMING MECHANISM 2Sheets-K-Sheet l Filed DeC. 4, 1967 F. A. WAGNER Oct. l, 1968 VARIABLEVALVE rI-IMING MECHANISM 2 Sheets-Sheet 2 Filed Dec.

tI- f4 //v VEA/Tof? FRANKAn/AGNER United States Patent O 3,403,663VARIABLE VALVE TIMING MECHANISM Frank A. Wagner, 1431 W. Catalpa,Chicago, Ill. 60640 Continuation-impart of application Ser. No. 625,890,Feb. 9, 1967. This application Dec. 4, 1967, Ser. No. 687,574 v 23Claims. (Cl. 123-90) ABSTRACT OF THE DISCLOSURE Hydraulic double liftervariable valve timing assembly for regulating the opening and closing ofintake and exhaust valves of internal combustion engines, the assemblyincluding a pair of fluid-coupled hydraulic lifters disposed coaxiallyfor relative reciprocal telescoping movement in response to a lobe cam,bearing against and controlling movement of one of said litters, the-degree of iiuid coupling between the two lifters and, thus, the timingof and extent of lifting by the lifters being a function of engine speedto provide optimum Valve operation at any given engine speed.

This application is a continuation-in-part of co-pending applicationSer. No. 625,890 tiled Feb. 9, 1967, now U.S. Patent No. 3,361,122,which is in turn a continuation-inpart of application Ser. No. 544,154,liled Apr. 26, 1966, now abandoned, which is in turn acontinuation-in-part of application Ser. No. 478,230, led Aug. 9, 1965,now U.S. Patent No. 3,277,874; and the present invention relatesgenerally to improvements in variable valve timing mechanisms findingutility in internal combustion engines. More particularly, the inventionis directed to engine-speed-controlled hydraulic mechanisms foroperating the exhaust and intake valves of such engines.

It is well known to those skilled in the art to which this inventionrelates that valve timing is very important in achieving maximum engineeciency, and that valve timing specially suited for high engine speedsis not the best timing for low engine speeds. It is therefore, the aimof the present invention to provide a variable valve timing mechanism ofimproved and simplified structure which will operate automatically toopen and close the valves of an internal combustion engine in a `mannerto ensure maximum operating efficiency at loW speeds, high speeds, andat intermediate speeds.

It is a principal object of the invention to provide an automaticallyoperable engine-speed-controlled, hydraulic variable valve timingmechanism which is operative to vary the valve timing as a lfunction ofengine speed and to provide smooth operation and maximum efliciency overthe entire operating speed range of the engine.

Another object of the invention is to provide a novel combination of asingle lobed cam with a double hydraulic lifter assembly to vary thevalve timing automatically as a function of engine speed while providingmaximum operating efficiency over the complete operating speed ran-ge ofthe internal combustion engine.

Still another object of the invention is to provide improved hydrauliccoupling means for interconnecting two lifters of a valve lifterassembly, in which assembly the degree or extent of coupling isautomatically a function of engine speed.

A related object of the invention is to provide a double lifter elementvalve control mechanism functioning in combination and cooperation withan improved iluid flow gating means responsive to the relative axialpositions of valve lifter elements of the hydraulic assembly.

Yet another object of the invention is to provide an improved automaticvariable valve timing mechanism in which compression forces applied to aspring of the mech- 3,403,663 Patented Oct. 1, 1968 ice anism arecontrolled through variable uid porting means which regulate the fluidcoupling between the two lifter elements of the assembly.

Another object of the invention is to provide a hydraulically controlledvalve timing mechanism which includes a pair of spring-stressed lifterelements, a uid chamber, and porting means which automatically cooperateto control oil passage into an-d from the chamber, to control the degreeof uid coupling of the two lifter elements and to vary this coupling asa 'function of engine speed, thereby to provide optimum valve timing atany given engine speed.

A related object of the invention is to provide ahydraulically-controlled variable valve timing mechanism for internalcombustion engines in which the compression-opposing properties of acompression-resisting spring, in cooperation with fluid coupling andporting means, precludes substantial spring compression at high enginespeeds while permitting compression at lower engine speeds.

Yet 'another object of the invention is to provide an improved variablevalve timing mechanism including an outer lifter and an inner lifteran-d in which the inner lifter is axially reciprocal within the outerlifter but Within precisely controlled longitudinal limits, one limitdefining a position assumed only at low engine speeds and another limitdefining a position assumed at high engine speeds, and in which thepositioning is variable innitely between the two extremes.

It is an important object of the invention to provide in an internalcombustion engine avariable valve timing mechanism utilizing but asingle cam lobe, but automatically regulated, through cooperating springforces and iiuid ducts and portings, to provide valve opening and timingwhich is precisely a function of and directly related to engine speeds.

Still another object of the invention is to provide an improved variablevalve timing mechanism including a pair of Huid-coupled inner and outerlitters in relatively reciprocal disposition and arranged to obviatemechanical bottoming of the inner on the outer lifter.

A related object of the invention is to eliminate objectional enginenoises associated with the physical, mechanical contacting of lmovingvalve lifting elements.

Another object of the invention is to provide a novel metering valve forsupplying lubricating uid to the valve push rod.

Other and further objects, aims and advantages of the invention willbecome apparent from a reading of the following specification taken inconjunction with the drawings in which:

FIGURE l is a semi-schematic illustration of the lifter assembly and camof one embodiment of the invention with parts broken away and in sectionand illustrating the mechanism of the lifters and showing the outerlifter in the position assumed at minimum height or lift of the camlobe;

FIGURE 2 is a View similar to that depicted in FIG- URE l but showingthe internal valve lifter in the maximum height or lift position assumedduring slow engine speeds, and including a schematic representation of asector diagram' showing, in reference to different angular positions ofthe engine crank shaft, the times of opening and closing of an exhaustvalve, expressed in degrees pertaining to the valve timing andindicating the effective lifting height and pattern at high and lowengine speeds.

FIGURE 3 is a view similar to that illustrated in FIG- URE 2 butindicating the position of the inner lifter assumed at high enginespeeds and at maximum lift height of the cam lobe;

FIGURE 4 is an exploded View of the component elements of the valvelifter assembly of the valve timing mech-anism of one embodiment of theinvention;

FIGURE 5 is a schematic representation of the linkage between a push rodactuated through the mechanism of the invention, and a valve assembly;and

FIGURE 6 is a top plan view of the valve lifter assembly shown in FIGUREl.

The present invention represents an improvement over earlier filedcopending applic-ation Ser. No. 625,890, the instant invention utilizingfewer mechanical parts and producing significantly less noise. The checkValve of earlier mechanisms has also been eliminated. In the presentinvention, the variable valve timing is achieved, as et forthhereinafter, through the use of -a single lobed cam in contact with asingle lifted element. In accordance with the practice of the presentinvention the valves and valve-actuating elements coact and cooperate toattain, in a greatly simplified manner, optimum valve cycling over abroad range of engine speeds.

The present invention is not limited in its applicability to anyparticular internal combustion engine but is generally useful in allsuch types of engines including overhead valve engines and engines inwhich the valves are located in the block. The invention also findsutility in engines in which the valve-operating cam shaft is disposedadjacent or over the cylinder head.

For purposes of illustrative disclosure, and not by way of limitati-on,the operation of the improved variable timing mechanism of the inventionwill be described herein with reference to an engine having overheadvalves, as illustrated schematically in FIGURE 5. The engine itself maybe considered conventional and includes a core or block in which thecylinders are provided, pistons which are reciprocally received withinthe cylinder, and cylinder heads fitted with suitable intake and exhaustvalves.

For optimum engine operation and for maximum power and smoothnessdifferent valve programming is required under different conditions. Atslower engine speeds, or at idling speeds, the intake valve shouldpreferably open as the piston reaches top dead center, and should remainopen until the piston reaches bottom dead center. Such operation ensuresfull intake of air and fuel mixtures. At the same time, exhaust valvesshould not open until the power stroke is completed and the pistonreaches bottom dead center. The exhaust valve should then remain openuntil the piston returns to top dead center, thus completing the cycle.

At high engine speeds a different valve timing cycle is desirable inorder to achieve maximum efliciency and power output. Intake valves mustopen sooner and close later, since the high velocity of air and fuelrushing into the combustion chamber will cause such air and fuel tocontinue to enter the chamber even after the piston has passed thebottom dead center. At higher engine speeds the exhaust valve ispreferably timed to open considerably before the piston reaches thebottom dead center, or prior to completion of the power stroke, andremains open until the piston has passed the top dead center point. 1tthus becomes possible to scavange the combustion gases from thecombustion chamber. In general, the higher the engine speed, the greateris the fraction of the cycle time during which the valves should beretained open.

However, engines with valves timed for high speed operation will notoperate satisfactorily at lower speeds. For example, at low enginespeeds the opening of the intake valve at a position before top deadcenter is reached will cause exhaust gases to be discharged through theintake port. M-oreover, as the piston passes bottom dead center, it willpush out a portion of the intake mixture, thus reducing the overalleffective charge. In a similar manner, the premature opening of theexhaust valve robs the engine of a full power stroke, and theover-extended open period of the valve reduces the intake charge. Anyadditional objectionable feature is that carb-onization of thecombustion chamber and of the intake valve will occur. Thus, an enginewith a predetermined valve timing will give satisfactory performanceonly within a given limite speed range.

In a typical low speed timing cycle there is relatively small timeoverlap of the exhaust and intake valves. In contrast, in a timing cyclefor high speed engine operation the periods of opening exhaust valvesand intake valves are much greater as is the overlap of the open periodsof these valves. It is possible through the present invention to obtainthe advantages of both low speed and high speed timing, and ofintermediate timing, in a single internal combustion engine having asingle camming lobe, thus enabling the engine to operate efliciently andlat maximum power over a wide range of engine speeds.

The aims and object of the invention are accomplished by providing in anautomatic variable valve timing mechanism a single lobed cam incombination with an improved double lifter assembly, the lifters of theassembly being disposed in telescoping relationship and being coupled,variably, through a fluid medium. The extent of coupling or interlockingof the two lifters is a function of fluid porting which is in turn adirect function of engine speed. At relatively high engine speeds noappreciable oil volume is discharged from the fluid cavity between thelifters so that the lifter elements become locked together through theincompressible column of oil in the chamber. In this locked position,the inner lifter is displaced upwardly with respect to the base of theouter lifter through the interaction and cooperation of a spring elementand fluid porting means whereby, in effect, a greater degree of liftingis realized at the higher engine speeds. At low engine speeds there isadequate time during the camming cycle for fluid to escape from withinthe chamber between the two lifter elements so that the inner lifterapproaches closer to the base of the outer lifter to provide, in effect,a shorter lifter element. At intermediate speeds, the actual liftingwill be a composite or hybrid of the two above-described modes ofoperation. Thus, for any particular engine speed, optimum conditions ofefficiency and power are realized.

Referring more particularly to the drawings, there is shown in FIGURES1, 2 a'nd 3, for the purpose of illustrative disclosure, a preferredembodiment of the variable valve timing mechanism of the invention,incorporating the teachings thereof. The timing mechanism 10 includes adouble lifter assembly 12 and a cam 14, the latter being fixed on a camshaft 16 for rotation therewith.

The double lifter assembly 12, shown in detail in FIG- URES 1 through 3and depicted in the exploded view, FIGURE 4, is slidably disposed forreciprocating action in a fixed body or block 20. The lifter assembly 12itself includes a generally cylindrically shaped outer lifter 24 havinga base wall or oor 28 which is normally supported on and rides on thecam 14. An inner lifter 32 is coaxial with a'nd slidably supportedwithin the outer lifter 24. A spring clip 36 (FIGURE 6) carried in aninternal annular groove or recess 38 near the upper end of the outerlifter precludes inadvertent separation of the two principal elements ofthe lifter assembly.

Referring more particularly to the inner lifter 32, in the preferredembodiment of the invention illustrated, the inner lifter comprises, asseen most clearly in FIGURE 4, a cup-shaped body 42 of generallycylindrical external form and including a top wall 44 and a dependingannular side wall 48 defining a downwardly opening chamber or cavity 52.The side wall 48 of the inner lifter is formed with a through port ororifice 56, and the wall 48 itself is undercut to provide a groove orduct 60 which intersects the port 56 and extends generally along aportion of the vertical expanse of the inner lifter 32 between the upperand lower limits thereof. The duct 60 has a variable or inconstant crosssectional area as defined by horizontal sections taken at verticallyspaced positions along the length of the duct 60, the cross sectionalarea increasing from an upper extremity 62 of the duct 60 downwardly.While the duct 60 may take various configurations or physical forms, inthe particular exemplary structure depicted in FIGURE 4, lthe duct is'atroughlike declivity formed to extend longitudinally along and radiallyinwardly of the wall 48 of the inner lifter 32, with trough depth at amaximum value at the location ofthe communicating through port y56. Thewalls 64 and 66 of the duct, as shown, constitute curved surfaces with aradius of curvature of about 2'1/2 inches, and maximum depth of the ductis, in the particular embodiment of the invention illustrated, about`0.030 inch. The parameters are not critical and, in the light of thepresent teachings, those skilled in the art will be able to apply thepresent invention to all types of valving systems, without exercisinginventive faculties.

' The top wall or head portion 44 of the inner lifter 32 is formed witha socket 70 extending axially inwardly of the top surface 74 of thelifter 32 for receiving in supporting engagement a push rod 78.Lubrication at the rounded base of the push rod 78 is provided through apassage 84 in the head 44 of the inner lifter and communicating with thechamber 52. As indicated schematically in FIGURE 5, the push rod '78 isconnected through conventional linkage, as for example, a rocker pin `92and a rocker cam 94 assembly, to stress against a valve stem 98. Duringoperation of the engine the push rod acts, in the conventional manner,to overcome the pressure of the valve return spring which is retainedbetween a fixed wall 102 and a spring seat 104 keyed 106 on the valvestem 98, to open the valve.

The outer lifter 24 is reciprocably slidable in the block 20 of theengine and is generally cylindrical or tubular in form with an integralbase 28 which, as previously described, rides upon the cam 14.Intermediate its opposed ends the cylindrical shell or wall of the outerlifter 24 is cut away to provide an annular groove 120 extendingradially inwardly from the periphery of the wall 110 `as seen mostclearly in FIGURE 4. The annular grooved portion of thelifter shell orwall 110 is provided with an opening or port or ports 124 extendingthrough the wall of the outer lifter, the ports 124 communicating withan oil supply and return channel and an oil line `132 in the block 20.The other end of the port 124 communicates with an annular passage 136formed between the body 52 of the inner lifter and the wall 110 of theouter lifter.

The inner lifter 32 is reciprocably slidable axially within the outerlifter 24, abutting contiguous wall surfaces of the lfters beingdimensioned for telescoping action. Coaxial with the axiallyreciproca'bly shiftable telescopingly coupled inner and outer lifters 32and 24 in the elongated chamber 140 and extending therewithin is a coilspring 142 supported at its lower end of the base 28 of the outer lifter24 and resiliently urging the inner lifter 32 upwardly through forcesapplied to the underside 144 of the top wall 44 thereof. Interposedbetween the upper end of the spring 142 and the underside 144 of the topwall 44 ofthe inner lifter 32 is a disc-like oil metering plate 154having formed in its top face to extend between a center region and aperipheral limit of the plate an open-ended groove-like slot 158communicating with an annular channel 160 defined between a' peripheralannular wall of the plate 154 and a radially outwardly spaced facingwall portion of the inner lifter 32, whereby the assembly establishes avolume-limiting fluid flow path between the oil chamber 140 and, throughthe head passage 84, a central bore 164 in the push rod 78.

yAs described above and as illustrated in FIGURES l through 3, theprincipal outer wall surface of the inner lifter 32 is in sliding butfluid-sealing engagement with the inner surface 174 of the wall 110 ofthe outer lifter. However, in the region of the duct 60 there is anautomatically variable zone of controlled fluid passage constitutingfluid venting and input means, the critical passage 60 between the walls170 and 174 establishing controlled fluid zone from the fluid inlet port124 in the 6 wall 110 of the outer lifter 24 and the through port 56 inthe wall of the inner lifter 32 to the central chamber or oil reservoir140. The fluid conduits or passage 130 in the block 20, thecommunicating annular channel 136, the bore 124 through the wall 110 ofthe outer lifter 24 and the passage 56 through the wall 180 of the innerlifter 32 each presents a fixed and invariable cross section to the flowof uid between the oil line 132 and the chamber or fluid reservoir 140.In contrast, the cross sectional area presented by the duct 60 dependsupon and is a direct function of the relative axial positions occupiedby the inner and outer litters. Since the cross sectional area of theduct or groove 60 is a maximum in the region of its intersection withthe port 56 and decreases progressively as the duct 60 projectsupwardly, maximum rate of fluid iiow through the duct ywill take placewhen, during reciprocating movement of the inner lifter 32 within theouter lifter 24, the port 56 most closely approaches an axial positionat or on a horizontal line with the communicating channel 136. In theembodiment of the invention illustrated, this condition obtains when theinner lifter 32'is at an upward extreme-of travel with respect to theouter lifter 24 (FIGURE 3). With downward movement of the inner lifter32 within the outer lifter 24 the cross section of the duct 60, at itsposition opposing the channel 136, decreases and uid escape from ordischarge from the cavity 140 is restricted, becoming a minimum when theinner lifter reaches a downward limit of its travel (FIGURE 2). Therestricted ilow serves to damp the downward motion and obviates shocks.

The operation of the variable valve timing mechanism is furtherdescribed below with reference to FIGURES l, 2 and 3. Referring first toFIGURE l which depicts the valve lifter 24 engaging the cam 14 at theheel portion 190, and considering first the case of low engine speedoperation, with the parts positioned as illustrated in FIGURE l, thepressure of the valve spring 100 transmitted to the inner lifter 32 isat a minimum and the opposing pressure of the internal spring 142 isadequate to bias the inner lifter 32 to its upwardly extreme positionagainst the stop or spring clip 36. In this position the duct 60 betweenthe lifter walls provides a maximum cross section and the most free orunrestricted uid communication or fluid passage between the internalcavity 140 within the litters and the passage 130 in the block.

As the cam shaft 16 rotates, the cam lobe 14 revolves, and as the highportion 194 engages the outer lifter 24, the lifter is forced upwardly.Concurrently, compressive force is applied to the spring 142 tending tomove the inner lifter downwardly relative to the outer lifter as theouter lifter rises. Upon consideration of the structure described, it isreadily apparent that in order for the inner lifter to move downwardlywithin the outer lifter from the position shown in FIGURE l to theposition shown in FIGURE 2, fluid must be dispelled or released from theannular cavity or chamber 140. While some fluid may be dispelled throughthe slot 158 in the oil metering plate 154 to the push rod 78, suchdischarge is exceedingly limited and inadequate to permit appreciabledownward shifting of the inner lifter. The major volume of fluid to bedischarged from the chamber 140 must escape through the port 56 and thecommunicating duct 60 and then through the channel 136 and the bore 24to the passage 130.

Since the inter-wall clearance aflorded by the duct or groove 60 islimited, the duct constitutes a fluid control port, and a finitepre-determined time is required to permit sufficient fluid to escapethrough this port so that the internal lifter 32 may move toward thebase wa'll 28 of the outer lifter, to the position shown in FIGURE 2.The effective cross section of the duct 60 decreases as the inner liftermoves downwardly, and the parameters of the mechanical system describedare such that at low engine speeds there is adequate fluid escape timeto permit the downward displacement of the inner lifter 32.

However, at high engine speeds (FIGURE 3) there is insufficient time,and thus the upward lifting or displacement of the push rod 98 at thehigh lobe portion of the camming cycle is less at low engine speeds thanis the displacement at a corresponding portion of the cycle but athigher engine speeds.

That is, at high engine speeds and with the outer lifter riding on theheel portion 190 of the cam 14, the relative positioning of the internalor inner lifter 32 is the same as at low engine speeds and asillustrated schematically in FIGURE 1. However, at such engine speeds,as the cam rotates and the high lift portion 194 of the cam engages andpushes upwardly on the outer lifter, there is insufficient time topermit the discharge of appreciable fluid from the chamber 140 throughthe passage or duct 60. As a result, the inner lifter 32 remains in itsupwardly displaced position and in substantial abutment against thespring clip 36 throughout the camming cycle. The significant practicaleffect at such high engine speeds is to lift the internal lifter 32 andits abutting push rod 98 earlier in the cycle and to a higher upperlimit and to hold the valve 202 in an open position for a greaterfraction of the camming cycle. At high engine speeds and associated highannular rotation of the cam shaft 16, the intake and exhaust valves ofthe engine will open sooner and close later than at low engine speeds,the fluid medium in the annular cavity 140 constituting a positivecoupling or interlock between the inner and outer lifters at high enginespeeds.

For purposes of illustrative disclosure, and not by way of limitation,for the preferred cam contour illustrated, note FIGURE 2 which depictsthe times of opening and closing of valves both for slow speed and forhigh speed engine operation. Recognizing that the cam shaft travels oner.p.m. for every two revolutions of the crank shaft, it is clear that,in the preferred arrangement illustrated, for low engine speed operationthe intake and exhaust valves will open and close for about equal timeperiods. At idling speeds the valve open time would be about 230. Athigh engine speeds the valves will open sooner and close later, and inthe preferred cam lobe illusrated, the valves will open 0.040 "to 0.060sooner, so that for engine speeds of about 1800 r.p.m. the valve opentime is about 324. The schematic diagram of FIGURE 2 reppresents intakevalve operation; exhaust valve operation would be similar, but oppositein phase. In the high lift portion of the cam illustrated schematicallyin FIGURE 2, the outer line represents the actual physical limit of themechanical cam, and comprises the effective cam contour at high enginespeed. The dotted or phantom line symbolizes the effective cam contourat low engine speeds, that is, when there is sufficient time to permitfluid escape and to allow the inner lifter to move toward the base wallof the outer lifter. In the preferred system and cam described, thedifference in the maximum lift is, as indicated in FIGURE 2, 0.060 inch.At intermediate engine speeds the effective cam lobe contour will fallin between the two limits illustrated in FIGURE 2. Under suchconditions, the intake and exhaust valve timing cycle is a composite ofthe two extremes. Thus, in accordance with the practice of the presentinvention, it is possible to obtain, in a single engine and with asingle cam lobe, the advantages of low speed and of high speed timingand of intermediate timing ensuring efficient engine operation atmaximum speeds, at low speeds, and at intermediate speed ranges.

While one preferred commercial embodiment of the novel variable valvetiming mechanism of the invention has been illustrated and described, itis understood that the same is capable of modification and that suchmodifications may be made without departure from the spirit and scope ofthe invention. For example, whereas in the particular embodiment of theinvention illustrated the walls which define the duct take the form of apair of curved surfaces intersecting along a radially inwardlydisplaced, curved, longitudinally extending line, many otherarrangements will, in the light of the present teachings and disclosure,be obvious to those skilled in the art. Simple equivalents include flatwalls as well as a single curved wall. It is also contemplated that theduct or groove may be formed in the wall of the outer rather than theinner lifter, and that the fluid flow control duct may be formedpartially in the inner and partially in the outer lifter.

While disclosures of preferred embodiments of the method and of theapparatus of the invention have been provided, it will be apparent thatnumerous modifications and variations thereof may be made withoutdeparting from underlying principles of the invention. It is therefore,described by the following claims to include within the scope of theinvention all such variations and modifications by which substantiallythe results of this invention may be obtained through the use ofsubstantially the same or equivalent means.

What is claimed is:

1. In an engine-speed-controlled cam-actuated automatically variablemechanism for opening valves of an internal combustion engine andincluding:

a cam having a cam surface,

a fixed body having a fluid supply passage,

a pair of fluid-coupled lifters arranged within said body in coaxialsliding engagement and having wall portions disposed for relativetelescopic axial movement,

said lifters comprising an outer lifter abutting and following said camsurface and an inner lifter in an out-of-contact relation with said camsurface and engaging a push rod for opening a valve of an engine,

said lifters defining therebetween a chamber adapted to contain a bodyof fluid comprising fluid means coupling one of said lifters to theother,

a wall of said outer lifter having through fluid inlet meanscommunicating with said fluid supply passage in said fixed body,

passage means connecting said fluid inlet means to said chamber forintroduction of fluid thereto;

the improvement wherein said passage means comprises an orice extendingtransversely through a wall of said inner lifter and communicating withsaid chamber,

said orifice intersecting a fluid-ilow-limiting duct of variable crosssectional area formed between and extending longitudinally along opposedfacing surfaces of said wall portions of said lifters and communicatingwith said through fluid inlet means in said wall of said outer lifter,

said duct being disposed to extend generally in a direction oftelescopic axial movement of said lifters and an effective crosssectional area of said duct being correlated with relative axialpositions assumed by by said inner and said outer lifters during axialdisplatement of said lifters relative to one another;

whereby said orifice and said duct constitute, in combination,

porting means for controlling the rate of discharge of fluid from saidchamber during axial displacement of said lifters relative to oneanother and for controlling the degree to which axial reciprocalmovement of said inner lifter coincides with and duplicates axialreciprocal movement of said outer lifter on said cam,

the degree of fluid coupling of said lifters being thereby a function oflinear displacement velocity of said outer lifter in response to camaction thereagainst, and

spring means urging one end of said inner lifter against said push rodand biasing an opposite end of said inner lifter to an out-of contactposition with respect to a base wall of said outer lifter.

2. The structure as set forth in claim 1 wherein said 75 duct comprisesa trough-like longitudinally disposed dcclivity formed toextend radiallyinwardly of` a bounding wall surface of one of said. lifters landbridged by an opposing f avcingwall of the other of said lifters.

3. The structure asset forth in claim 1 .wherein said duct definesalzone which isl of-.inconfstant cross-sectional area .asrneasuredtransversely of said duct at spaced positions along its length. g g 4 oo, l

4. The structure as set forth in claim 2 wherein said cross-sectionalarea increases along a path extending from an upper extremity of saidduct downwardly toward said oriticetherebelowf p v 5. The structure asset forth in claim 1 wherein a horizontal; cross-section of said ductis.substantially triangular in peripheral contour.`

6. The structure as set forth in claim 1 whereinia cross i section ofsaid duct defines a peripheral cont'our consisting of three lines eachconnected at its ends to two other lines to form a'n endless -path, twoof said lines being concave andone being convex, as viewed from aposition within said path. v

7. The structureas setforth in Yclaim 1 whereinsaid Yductis bounded ontwo sides lby a pair of surfaces intersecting along a generallyvertically extending radially inwardly arcing line to define asubstantiallyV V-shaped groove in a wall of said lifters.

8. The structure as set Vforth in claim 1 wherein said duct Acomprisesafluid conduitvdeflned by a wall of one of said lifters and atrough-like declivity formed in a facing wall of the other of saidlifters at said wallportions thereof disposed for relative telescopicaxial movement.

9. The structure as set forth in claim 1 and further comprising meteringvalve means for control of ow of lubricating fluid from said chamber toa base of said push rod engaged by said inner lifter.

10. The structure as set forth in claim 9 wherein said metering valvemeans comprises a disc-like plate horizontally disposed to abut an upperend wall of a cavity extending axially inwardly and upwardly of saidinner lifter from a base portion thereof,

said plate defining between an encircling peripheral wall thereof and aninner vertically extending cylindrical wall of said inner lifter channelmeans in fluid flow communication with said chamber,

said plate having formed therein to extend between a center region of atop surface of said plate and a peripheral limit thereof an open-endedgrooved communicating with said channel means,

said upper-end wall of said inner li-fter having formed to extendvertically therethrough a port constituting a iluid ilow path between abase of said push ,rod and said groove for delivery of lubricating fluidfrom said chamber to said push rod and for flow-regulated discharge ofuid from said chamber.

11. The structure as set forth in claim 1 wherein said spring-means isconfined in said chamber to extend axially between said base wall ofsaid outer lifter and an upper end wall of said inner lifter.

12. The mechanism as set forth in claim 1 wherein said chamber betweensaid outer and inner lifters includes a well-like cavity in the base ofSaid -outer lifter, and wherein said inner lifter has an open-endedhollow core coaxial with and opening into and communicating with saidcavity, said hollow core together with said cavity constituting an oilreservoir of variable volume.

13. The structure as set Iforth in claim 1 wherein each said inner andsaid outer lifters comprises a generally cylindrical container open atone end, said lifters being disposed telescopingly to inter-engage infacing open-end relationship to define a chamber extending coaxiallywithin said lifters and bounded by telescopingly engaging walls of saidlifters and by opposed end-walls thereof.

14. The structure as set forth in claim 12 wherein said spring means isdisposed axially within said chamber and comprises a coil springstressingly and resiliently abuting 10 at opposed axial extremitiesthereof *corresponding said opposed end walls of said lifters to biassaid end walls axially outwardly of one another.

1S. The structure as set forth in claim 1 wherein'lluid contained insaid chamber between said lifters comprises means vprecluding downwardmovement of said inner lifter Awithinsaid outer lifter'in the absence offluidescape from said chamber, a rate of said downwardmovement beingregulated by a rateat which said lluid isrdispelled from said chamberthrough said porting means.v '16. The structure as set forth in claim 1wh'erein said spring means is strongly resistent to and vopposes axialcompression and comprises an opposing structural element to be overcomeduring relative downward movement of said inner lifter within said outerlifter as said outer lifter engages a high-lift portion of said cam, andwherein said porting means comprises iluid-tlow-limiting meansregulating iluid discharge from said chamber and precluding rapidrelative downward movement from said inner lifter within said outerlifter and toward a base wall thereofas said louter lifter engages saidhigh lift portion of said cam,

said spring means being effective rapidly to force said inner liftertoward an upper limit position when said lower lifter engages a low-liftportion of said cam; whereby said mechanism automatically providessmaller cycle fractions of Valve openingsat lower engine speed andlarger cycle fractions of valve openings at higher engine speed, therebyeffecting earlier opening and later closing of intake and exhaust valvesat higher engine speed and later openings and earlier closing of saidvalves at lower engine speed.

17. The structure as set forth in claim 1 and further comprising aretainer ring carried by and projecting radially inwardly of a verticalwall of said outer lifter at an upper portion thereof, said ringconstituting mechanical stop means limiting upward travel of said innerlifter within said outer lifter in response to spring pressure urgingsaid inner lifter upwardly of a base of said outer lifter. i

18. The mechanism as set forth in claim 1 wherein said porting meansregulating volume rate of lluid discharged from said chamber during camaction against said outer lifter limits volume rate of fluid exhaustfrom said chamber, volume of fluid exhaust from said chamber as afunction of time varying inversely as the angular velocity of said camshaft and a lobe of said cam during operation of said engine;

whereby at slow engine speed, input to and exhaust of iluid from saidchamber permits reciprocal movement of said inner lifter within saidouter lifter, while at high engine speed, time lag and restricted fluiddischarge from said chamber through said porting means precludeindependent movement of said outer and inner lifters and establish adegree of fluid coupling, engagement and inter-locking between saidlifters,

said degree of coupling, engagement and inter-locking being proportionalto and increasing with engine speed.

19. The mechanism as set forth in claim 1 wherein said duct comprises anaperture between walls of said inner and said outer lifters and denes afluid passage zone of a variable cross-sectional area, said area beingcorrelated with relative axial positions assumed by said inner and saidouter lifters during said axial displacement 1 1 1,2 21. In anengine-speedcontrolled cam-actuated autowith said fluid inlet meansformed in said wall of matically variable mechanism for opening valvesof an insaid outer lifter, Y ternal combustion engine and including: owrate of fluid through said gating zone being coracam having a camsurface, related with relative vaxial positions assumed by a xed bodyhaving a uid supply passage, 5 said inner and said outer lifters duringaxial ldisa pair of uidcoupled-lifters arranged within said v placementof said litters 'relative to one ai'iother;

body in coaxial sliding engagement and having wall whereby said slotconstitutes in combination with said portions disposed for relativetelescopic axial movebore uid ow control passage means between saidment, y uid inlet means and said chamber. A said lifters comprising anouter lifter abutting and follo 22. The vstructure as set forth in claim2 wherein maxi'- lowing saidl cam surface and an inner lifter in an mumdepth of said duct as measured radially inwardly of -ou't-of-contactrelationship with said cam surface arid a bounding wall surf-ace of`said one of said lifters is engaging a push rod for opening a valve ofan enabout 0.030 inch. gine, 23. The structure as set forth in claim 6wherein said said lifters dening therebetween a chamber adapted 15surfaces are curved surfaces formed on a radius of about to contain abody of uid comprising uid means 21/2 inches. l coupling one of saidlifters to the other, References Cited a wall of said outer lifterhaving through fluid inlet UNITED STATES PATENTS {man s CommumcatlngWlth Sald uld Supply passage 1,3 53,993 9/1920 Fisher 123 90 m sad xedbody 20 2 484109 iti/1949 M k l the improvement therein one of saidinner and said Y einec e Ugg-90 oute Ylifte* 's vformed to i ovid alon av ticall 2614547 10/1952 Memecke 123-90 f *S 1 Pf e g er Y 2,791,9935/1957 Hubbard et ai; 12s-9o extending wall surface thereof a cut awayportion 2,931,347 4/1960 Williams 12? 90 establishing an elongated slotof variable cross-sec- 2r 3,058,454 1071962 Goncalves 123 90 tional areadefining a fluid ow gating zone between 0 3,142,290 7 /1964 Lesher 123,90 said lifters at contiguous surfaces thereof and longi- 3,277,87410/1966 Wagner 123 90 tudinally therealong, 3,361,122 1/ 1968 Wagner123-90 said slot intersecting a through bore formed in a vertical wallof said inner lifter and communicating AL LAWRENCE SMITH PrimaryExaminer-

